How Can I Send You A Christmas Present, But For You Not To Cheat and Open It? … Time-lock Puzzles and Proof of Work
So how might we make sure that someone does not open their present until Christmas Day? Well, one way is to get them to do some work to open it, and that we know it will only be done within a certain amount of time — such as with the days there are until Christmas. So, let’s look at an area called Proof of Work, and where Victor (the verifier of the work) wants Peggy (the prover of the work) to do some work for him. We have all seen the effects of Proof of Work within the Bitcoin network, but let’s see if there are better methods. The first method we will look at is hashing something multiple times— and which is a task that can normally only be done in a sequential way, so you could put away your GPUs for just now.
Hashing
This method is defined here.
One method is to get the receiver to perform some work to find the encryption key. For example if we wanted to lock it down for one hour we could take a seed value, and then continually hash it for a given amount of time that we thing the recipient would required to generate the same key. This would then generate the same key, if the sender and recipient share the number of iterations of the hash used. We can then tell the receiver the seed value…
